Trust Center#

This file describes the routines used by the Trust Center to manage devices in the network. The Trust center decides whether to use preconfigured keys and manages passing out keys to joining and rejoining devices. The Trust Center also sends out new keys and decides when to start using them.

See trust-center.h for source code

Variables#

Control the policy that the Trust Center uses for determining whether to allow or deny requests for application link keys between device pairs. When a request is received and the policy is EMBER_ALLOW_TC_LINK_KEY_REQUEST_AND_SEND_CURRENT_KEY, the TC will generate a random key and send a copy to both devices encrypted with their individual link keys.

Functions#

emberBroadcastNextNetworkKey(EmberKeyData *key)

Broadcast a new encryption key but does not tell the nodes in the network to start using it.

emberSendUnicastNetworkKeyUpdate(EmberNodeId targetShort, EmberEUI64 targetLong, EmberKeyData *newKey)

Send a unicast update of the network key to the target device. The APS command will be encrypted using the device's current APS link key. On success, the bit ::EMBER_KEY_UNICAST_NWK_KEY_UPDATE_SENT will be set in the link key table entry for the device. When a successful call is made to emberBroadcastNetworkKeySwitch(), the bit will be cleared for all entries.

emberUnicastCurrentNetworkKey(EmberNodeId targetShort, EmberEUI64 targetLong, EmberNodeId parentShortId)

Send the network key to the target device. The APS command will be encrypted using the device's current APS link key. The call fails if no link key is available.

Broadcast a switch key message to tell all nodes to change to the sequence number of the previously sent Alternate Encryption Key.

emberTrustCenterJoinHandler(EmberNodeId newNodeId, EmberEUI64 newNodeEui64, EmberDeviceUpdate status, EmberNodeId parentOfNewNode)

Allow the application running on the Trust Center (which is the coordinator for ZigBee networks) to control which nodes are allowed to join the network. If the node is allowed to join, the trust center must decide whether to send the Network Key encrypted or unencrypted to the joining node.

emberBecomeTrustCenter(EmberKeyData *newNetworkKey)

Cause a coordinator to become the Trust Center when it is operating in a network that is not using one. It will send out an updated Network Key to all devices that will indicate a transition of the network to now use a Trust Center. The Trust Center should also switch all devices to using the new network key with a call to emberBroadcastNetworkKeySwitch().

uint8_t

Control the policy that the Trust Center uses for determining whether to allow or deny requests for Trust Center link keys.

emberSendRemoveDevice(EmberNodeId destShort, EmberEUI64 destLong, EmberEUI64 deviceToRemoveLong)

Send an APS remove device command to the destination. If the destination is an end device, this must be sent to the parent of the end device. In that case, the deviceToRemoveLong and the destLong will be different values. Otherwise, if a router is being asked to leave, those parameters will be the same. This command will be APS encrypted with the destination device's link key, which means a link key must be present.

emberSendTrustCenterLinkKey(EmberNodeId destinationNodeId, EmberEUI64 destinationEui64)

Send the trust center link key to a node.

Macros#

#define

A Trust Center device configuration bitmask example. The Trust Center is expected to be set up with a Network Key Preconfigured Link Key that is global throughout all devices on the Network. The decision whether or not to send the key in-the-clear is NOT controlled through this bitmask. It is controlled via the emberTrustCenterJoinHandler(...) function.

#define

A coordinator device configuration bitmask example. The coordinator is expected to be set up with a Network Key and a Preconfigured Link Key that is global throughout all devices on the Network. The decision whether or not to send the key in-the-clear is decentralized. Each individual router can make this decision via the emberTrustCenterJoinHandler(...) function.

#define
emberTrustCenterLinkKeyRequestPolicy emberTrustCenterLinkKeyRequestPolicies[emGetNetworkIndexForForkedGlobal()]
#define
emberAppLinkKeyRequestPolicy emberAppLinkKeyRequestPolicies[emGetNetworkIndexForForkedGlobal()]

Variable Documentation#

emberTrustCenterLinkKeyRequestPolicies#

EmberTcLinkKeyRequestPolicy emberTrustCenterLinkKeyRequestPolicies[]

Definition at line 249 of file stack/include/trust-center.h

emberAppLinkKeyRequestPolicies#

EmberAppLinkKeyRequestPolicy emberAppLinkKeyRequestPolicies[]

Control the policy that the Trust Center uses for determining whether to allow or deny requests for application link keys between device pairs. When a request is received and the policy is EMBER_ALLOW_TC_LINK_KEY_REQUEST_AND_SEND_CURRENT_KEY, the TC will generate a random key and send a copy to both devices encrypted with their individual link keys.

Generally, application link key requests may always be allowed.


Definition at line 261 of file stack/include/trust-center.h

Function Documentation#

emberBroadcastNextNetworkKey#

EmberStatus emberBroadcastNextNetworkKey (EmberKeyData * key)

Broadcast a new encryption key but does not tell the nodes in the network to start using it.

Parameters
N/Akey

A pointer to a 16-byte encryption key (EMBER_ENCRYPTION_KEY_SIZE). A NULL (or all zero key) may be passed in, which will cause the stack to randomly generate a new key.

To broadcast a new key, use emberBroadcastNetworkKeySwitch(), which is only valid for the Trust Center/Coordinator. It is not valid when operating in Distributed Trust Center mode.

It is up to the application to determine how quickly to send the Switch Key after sending the alternate encryption key. The factors to consider are the polling rate of sleepy end devices and the buffer size of their parent nodes. Sending too quickly may cause a sleepy end device to miss the Alternate Encryption Key and only get the Switch Key message, which means it will be unable to change to the new network key.

Returns

  • An EmberStatus value that indicates the success or failure of the command.


Definition at line 84 of file stack/include/trust-center.h

emberSendUnicastNetworkKeyUpdate#

EmberStatus emberSendUnicastNetworkKeyUpdate (EmberNodeId targetShort, EmberEUI64 targetLong, EmberKeyData * newKey)

Send a unicast update of the network key to the target device. The APS command will be encrypted using the device's current APS link key. On success, the bit ::EMBER_KEY_UNICAST_NWK_KEY_UPDATE_SENT will be set in the link key table entry for the device. When a successful call is made to emberBroadcastNetworkKeySwitch(), the bit will be cleared for all entries.

Parameters
N/AtargetShort

The short node ID of the device to send a NWK key update to.

N/AtargetLong

The EUI64 of the node to send a key update NWK key update to.

N/AnewKey

A pointer to the new NWK key value.

On the first call to this function, the trust center's local copy of the alternate NWK key will be updated with the new value.

Both the short and long address of the device must be known ahead of time and passed in as parameters. It is assumed that the application has already generated the new network key and will pass the same key value on subsequent calls to send the key to different nodes in the network.

Returns

  • An EmberStatus value that indicates the success or failure of the command.


Definition at line 114 of file stack/include/trust-center.h

emberUnicastCurrentNetworkKey#

EmberStatus emberUnicastCurrentNetworkKey (EmberNodeId targetShort, EmberEUI64 targetLong, EmberNodeId parentShortId)

Send the network key to the target device. The APS command will be encrypted using the device's current APS link key. The call fails if no link key is available.

Parameters
N/AtargetShort

The short node ID of the device to send a NWK key to.

N/AtargetLong

The EUI64 of the node to send a NWK key to.

N/AparentShortId

The short node ID of the parent of the device to send a NWK key to.

Both the short and long address of the device must be known ahead of time and passed in as parameters. It is assumed that the application has already generated the new network key and will pass the same key value on subsequent calls to send the key to different nodes in the network.

Returns

  • An EmberStatus value that indicates the success or failure of the command.


Definition at line 150 of file stack/include/trust-center.h

emberBroadcastNetworkKeySwitch#

EmberStatus emberBroadcastNetworkKeySwitch (void )

Broadcast a switch key message to tell all nodes to change to the sequence number of the previously sent Alternate Encryption Key.

Parameters
N/A

This function is only valid for the Trust Center/Coordinator and will also cause the Trust Center/Coordinator to change its Network Key. It is not valid when operating in Distributed Trust Center mode.

Returns

  • An EmberStatus value that indicates the success or failure of the command.


Definition at line 165 of file stack/include/trust-center.h

emberTrustCenterJoinHandler#

EmberJoinDecision emberTrustCenterJoinHandler (EmberNodeId newNodeId, EmberEUI64 newNodeEui64, EmberDeviceUpdate status, EmberNodeId parentOfNewNode)

Allow the application running on the Trust Center (which is the coordinator for ZigBee networks) to control which nodes are allowed to join the network. If the node is allowed to join, the trust center must decide whether to send the Network Key encrypted or unencrypted to the joining node.

Parameters
N/AnewNodeId

The node ID of the device wishing to join.

N/AnewNodeEui64

The EUI64 of the device wishing to join.

N/Astatus

The EmberUpdateDeviceStatus indicating whether the device is joining/rejoining or leaving.

N/AparentOfNewNode

The node ID of the parent of the device wishing to join.

A default handler is provided and its behavior is as follows. A status of ::EMBER_DEVICE_SECURED_REJOIN means that the device has the Network Key, no action is required from the Trust Center. A status of EMBER_DEVICE_LEFT also requires no action. In both cases, EMBER_NO_ACTION is returned.

When operating in a network with a Trust Center and there is a Global Link Key configured, EMBER_USE_PRECONFIGURED_KEY will be returned, which means the Trust Center is using a preconfigured Link Key. The Network Key will be sent to the joining node encrypted with the Link Key. If a Link Key has not been set on the Trust Center, EMBER_DENY_JOIN is returned.

The ::EMBER_ASK_TRUST_CENTER decision has been deprecated. This function will not be called for a router or end device when operating in a Network With a Trust Center.

If the device is a router in a network that is operating in a Distributed Trust Center Security mode, the handler will be called by the stack.

The default handler in a Distributed Trust Center Security mode network is as follows: If the router received an encrypted Network Key when it joined, a preconfigured Link key will be used to send the Network Key Encrypted to the joining device (EMBER_USE_PRECONFIGURED_KEY). If the router received the Network Key in the clear, it will also send the key in the clear to the joining node (EMBER_SEND_KEY_IN_THE_CLEAR).

Returns


Definition at line 211 of file stack/include/trust-center.h

emberBecomeTrustCenter#

EmberStatus emberBecomeTrustCenter (EmberKeyData * newNetworkKey)

Cause a coordinator to become the Trust Center when it is operating in a network that is not using one. It will send out an updated Network Key to all devices that will indicate a transition of the network to now use a Trust Center. The Trust Center should also switch all devices to using the new network key with a call to emberBroadcastNetworkKeySwitch().

Parameters
N/AnewNetworkKey

The key data for the Updated Network Key.

Returns

  • An EmberStatus value that indicates the success or failure of the command.


Definition at line 228 of file stack/include/trust-center.h

emGetNetworkIndexForForkedGlobal#

uint8_t emGetNetworkIndexForForkedGlobal (void )

Control the policy that the Trust Center uses for determining whether to allow or deny requests for Trust Center link keys.

Parameters
N/A

The following is a good set of guidelines for TC Link key requests:

  • If preconfigured TC link keys are set up on devices, requests for the TC key should never be allowed (EMBER_DENY_TC_LINK_KEY_REQUESTS).

  • If devices request link keys during joining (i.e., join in the clear and set EMBER_GET_LINK_KEY_WHEN_JOINING) then it is advisable to allow requesting keys from the TC for a short period of time (e.g., the same amount of time "permit joining" is turned on). Afterwards, requests for the TC link key should be denied.


Definition at line 246 of file stack/include/trust-center.h

emberSendRemoveDevice#

EmberStatus emberSendRemoveDevice (EmberNodeId destShort, EmberEUI64 destLong, EmberEUI64 deviceToRemoveLong)

Send an APS remove device command to the destination. If the destination is an end device, this must be sent to the parent of the end device. In that case, the deviceToRemoveLong and the destLong will be different values. Otherwise, if a router is being asked to leave, those parameters will be the same. This command will be APS encrypted with the destination device's link key, which means a link key must be present.

Parameters
N/AdestShort

The short node ID of the destination of the command.

N/AdestLong

The EUI64 of the destination of the command.

N/AdeviceToRemoveLong

The EUI64 of the target device being asked to leave.

Returns

  • An EmberStatus value indicating success or failure of the operation.


Definition at line 281 of file stack/include/trust-center.h

emberSendTrustCenterLinkKey#

EmberStatus emberSendTrustCenterLinkKey (EmberNodeId destinationNodeId, EmberEUI64 destinationEui64)

Send the trust center link key to a node.

Parameters
N/AdestinationNodeId

The short address of the node to which this command will be sent.

N/AdestinationEui64

The long address of the node to which this command will be sent.

This function sends an APS TransportKey command containing the current trust center link key. The node to which the command is sent is specified via the short and long address arguments.

Returns

  • An EmberStatus value indicating success or failure of the operation.


Definition at line 297 of file stack/include/trust-center.h

Macro Definition Documentation#

EMBER_FORM_TRUST_CENTER_NETWORK_BITMASK#

#define EMBER_FORM_TRUST_CENTER_NETWORK_BITMASK
Value:
(EMBER_STANDARD_SECURITY_MODE \
| EMBER_TRUST_CENTER_GLOBAL_LINK_KEY \
| EMBER_HAVE_NETWORK_KEY \
| EMBER_HAVE_PRECONFIGURED_KEY)

A Trust Center device configuration bitmask example. The Trust Center is expected to be set up with a Network Key Preconfigured Link Key that is global throughout all devices on the Network. The decision whether or not to send the key in-the-clear is NOT controlled through this bitmask. It is controlled via the emberTrustCenterJoinHandler(...) function.


Definition at line 42 of file stack/include/trust-center.h

EMBER_FORM_DISTRIBUTED_TRUST_CENTER_NETWORK_BITMASK#

#define EMBER_FORM_DISTRIBUTED_TRUST_CENTER_NETWORK_BITMASK
Value:
(EMBER_STANDARD_SECURITY_MODE \
| EMBER_TRUST_CENTER_GLOBAL_LINK_KEY \
| EMBER_DISTRIBUTED_TRUST_CENTER_MODE \
| EMBER_HAVE_NETWORK_KEY \
| EMBER_HAVE_PRECONFIGURED_KEY)

A coordinator device configuration bitmask example. The coordinator is expected to be set up with a Network Key and a Preconfigured Link Key that is global throughout all devices on the Network. The decision whether or not to send the key in-the-clear is decentralized. Each individual router can make this decision via the emberTrustCenterJoinHandler(...) function.


Definition at line 55 of file stack/include/trust-center.h

emberTrustCenterLinkKeyRequestPolicy#

#define emberTrustCenterLinkKeyRequestPolicy
Value:
emberTrustCenterLinkKeyRequestPolicies[emGetNetworkIndexForForkedGlobal()]

Definition at line 250 of file stack/include/trust-center.h

emberAppLinkKeyRequestPolicy#

#define emberAppLinkKeyRequestPolicy
Value:
emberAppLinkKeyRequestPolicies[emGetNetworkIndexForForkedGlobal()]

Definition at line 262 of file stack/include/trust-center.h